Semiconductor Component with Plastic Housing, and Process for Producing the Same

ABSTRACT

A semiconductor component includes a plastic housing including: plastic outer surfaces; lower outer contact surfaces arranged on an underside of the housing; upper outer contact surfaces arranged on a top side of the housing that is opposite the underside; and outer interconnects electrically connecting the lower outer contact surfaces to the upper outer contact surfaces, the outer interconnects including a layer of solder arranged on conduction paths along an outer contour of the housing.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of prior application Ser.No. 11/246,454, filed Oct. 11, 2005, which claims priority under 35U.S.C. §119 and/or 365 to German Application No. DE 10 2004 049 654.4filed on Oct. 11, 2004, entitled “Semiconductor Component With PlasticHousing, And Process For Producing It,” both of which are herebyincorporated by reference in their entireties.

FIELD OF THE INVENTION

The invention relates to a semiconductor component with a plastichousing and to a process for producing it. In particular, the inventionrelates to a semiconductor component arrangement for stackingsemiconductor components with at least one semiconductor base component.The semiconductor base component has a housing which includes plasticouter surfaces. Outer contact surfaces for the application of outercontacts are arranged on an underside of the housing, and outer contactsurfaces for the stacking of a semiconductor component on the plastichousing of the semiconductor base component are arranged on a top sideof the housing, which is the opposite side from the underside.

BACKGROUND

Conventional semiconductor base components, as are known from Germanpatent publication No. DE 101 38 278, for the stacking of BGA or LBGAhousings (ball grid array or large ball grid array), are provided withadditional flexible rewiring sheets which have a larger area than thesemiconductor components to be stacked and project beyond the edge ofthe semiconductor components, so that they can be bent toward asemiconductor component of a semiconductor component stack arrangedbelow and can be electrically connected to the semiconductor componentarranged below via the flexible sheet.

A semiconductor module with semiconductor components stacked in this wayhas the drawback that the semiconductor components cannot be stackedwithin the minimum possible space, especially since the bent rewiringsheet also requires a minimum bending radius, without which there is arisk of microcracks forming in the rewiring lines arranged on therewiring sheet. Other conventional semiconductor base components have arewiring

substrate with outer contacts arranged on the underside of the rewiringsubstrate, and at least one semiconductor chip or a memory component,such as a DRAM (dynamic random access memory), is arranged in the centerof the rewiring substrate, on the top side of the rewiring substrate.

If a conventional semiconductor component of this type is to be used asthe semiconductor base component for a semiconductor module, only theedge regions of the rewiring substrate can be made available for theapplication of outer contacts of a stacked semiconductor component, ashas been described in German patent application DE 10 2004 009 056.Since the center of the rewiring substrate is taken up by thesemiconductor chip, the number and arrangement of outer contacts in thesemiconductor component to be stacked are greatly restricted, andconsequently a large number of known housing types, such as BGA or LBGAhousings, cannot be stacked on a conventional semiconductor componentwith rewiring substrate of this type.

SUMMARY

The invention relates to a semiconductor component with a rewiringsubstrate and a process for producing it, which can be used as asemiconductor base component. The invention further provides asemiconductor component in which any desired arrangement of outercontact surfaces can be provided on the top side, and a distribution ofouter contact surfaces on the underside of the wiring substrate for asurface-mountable semiconductor component which is independent of thearrangement of the outer contact surfaces on the top side is possible.The invention minimizes the space and area taken up by a semiconductorcomponent, in particular, to reduce the space taken up by a memorymodule composed of DRAM semiconductor components.

According to an exemplary embodiment, a semiconductor component includesa housing comprising plastic outer surfaces, which is equipped withlower outer contact surfaces arranged on an underside of the housing andwith upper outer contact surfaces arranged on a top side of the housingthat is the opposite side from the underside. To produce the connectionbetween the upper outer contact surfaces and the lower outer contactsurfaces, the plastic housing has outer interconnects. These outerinterconnects have a layer of solder that is arranged on conductionpaths along the housing outer contour.

This semiconductor component has the advantage that there is no need forany additional intermediate wiring substrates or rewiring sheets toconnect the outer contact surfaces on the top side to the outer contactsurfaces on the underside. Rather, the housing outer contour is utilizedto produce conduction paths on the plastic outer surfaces of the housingouter contour, which conduction paths are thickened with the aid of alayer of solder to form interconnects. Therefore, the plastic housingcompound or the plastic outer surfaces are used to generate conductionpaths. The space required to provide outer contact surfaces on the topside of the semiconductor component and to apply interconnects along theouter contour of the plastic housing with electrical connection to theouter contacts on the underside is thereby reduced. Moreover, theplastic housing per se already forms the substrate material for theseinterconnects and therefore performs a dual function, in that on the onehand the plastic housing embeds the components of the semiconductor chipand on the other hand on its plastic outer surfaces offers thepossibility of electrically connecting upper outer contact surfaces tolower outer contact surfaces.

This does not require the conduction paths already to have a continuousmetallization. Rather, a preferred embodiment of the invention providesa conduction path comprising particles of the plastic outer surfaces ofthe housing which are isolated from one another, and can be wetted byliquid solder material and are provided along a conductor path structureon the plastic outer surfaces. The particles which can be wetted bysolder material are arranged so close together in the region of theconduction paths that a liquid solder material can spread out or flowalong these conduction paths made up of electrically conductiveparticles that are isolated from one another. This embodiment of theinvention has the advantage that only electrically conductive particlesneed to be arranged distributed within the plastic housing compound andare partially uncovered to form conduction paths while remainingpartially anchored in the plastic housing compound. Consequently, theconducting particles not only form wettable support points for thesolder material but at the same time also anchor the solder material ofthe interconnects along the housing outer contour.

In a further embodiment of the invention, the conduction paths comprisea metal layer which is a few nanometers thick and can be wetted byliquid solder material. This wettable metal layer is arranged along thehousing outer contour on the plastic outer surfaces of the housing. Ametallic layer which is a few nanometers thick of this type asconduction path can be applied to the plastic outer surfaces of thehousing with the aid of sputtering, vapor deposition or plasmadeposition.

In a further variant of the conduction paths, these conduction paths maycomprise individual, wettable bonding wires, which are arranged fromouter contact surfaces on the top side of the plastic housing to contactterminal surfaces of a wiring substrate and are thickened with the aidof a liquid solder material, in such a manner that they bear closelyagainst the plastic housing along the housing outer contour.

If these bonding wires as conduction paths for liquid solder materialare arranged next to one another in pairs, it is possible to createsupply current paths or supply current interconnects via these bondingwires arranged in pairs with a strip of solder material arranged betweenthem, and these supply current paths or supply current interconnects aresuitable for increasing the supply of current to the semiconductorchips.

In a further preferred embodiment of the invention, the housingcomprises a wiring substrate on its underside. This wiring substratecomprises through-contacts arranged on its edge regions. On the top sideof the wiring substrate, these through-contacts form contact terminalsurfaces which are electrically connected to the outer interconnects onthe housing outer contour of the plastic housing. On the underside ofthe wiring substrate, the through-contacts are electrically connected,via a wiring structure, to the corresponding lower outer contactsurfaces. This embodiment of the invention has the advantage that thelarger interconnects do not have to be guided around the semiconductorhousing, but rather they can end at the contact terminal surfaces on thetop side of the wiring substrate, which are formed by thethrough-contacts. This increases the reliability of the structure ofouter interconnects of this type on the outer plastic sides of thesemiconductor component housing.

A further embodiment of the invention provides for the plastic of thehousing to comprise inclusions of an organometal compound. The metallicconstituents of this organometal compound are freely accessible and openin the conduction paths, such that they can be wetted by soldermaterial, and are then wetted by solder material. The advantage of thisembodiment of the invention is that the metallic constituents in theconduction paths on the outer sides of the semiconductor housing can beuncovered by the action of radiation, so that any desired conductionpath arrangements can be realized with the aid of irradiationtechnology. The irradiation device used may be laser beams, ion beams orelectron beams, in order to uncover the metallic constituents of theorganometal compounds for the conduction paths on the top side of theplastic housing compound.

In a further embodiment of the invention, it is provided that theplastic of the housing comprises inclusions of electrically conductivenanoparticles. These nanoparticles are arranged partially uncovered inthe paths and can be wetted by liquid solder material. Nanoparticles ofthis type may be fullerenes, which have a hollow sphere of hexagonallyarranged carbon atoms. These fullerenes in hollow sphere form arearranged in a concentration in the plastic housing compound which issuch that they do not cause an electrical short circuit within theplastic housing compound. On the other hand, the density of thefullerenes is sufficient for them to be partially uncovered in theintended conduction paths given a suitable irradiation treatment, sothat they are available for coating with solder material.

In addition to the fullerenes, nanoparticles of this type may alsoinclude nanotubes, which have a diameter of only a few nanometers but,as multi-walled nanotubes, may be up to a few millimeters long. Parts ofthese nanotubes are anchored in the plastic housing compound, whereasthese nanotubes are uncovered on the outer sides of the plastic housingin the region of the conduction paths, so that they form wetting andanchoring points for the soldering material.

The preparation of the wiring paths may include preparation of outercontact surfaces on the top side of the plastic housing compound, sothat after wetting with solder material on the top side, not onlyinterconnects are formed, but also outer contact surfaces of a suitablesize, the size and arrangement of which are matched to the size andarrangement of outer contacts for stacked semiconductor components. Thishas the advantage that no additional deposition processes are requiredfor arranging the outer contacts on the top side of the plastic housing,but rather the solder material can be positioned on the prepared outercontact surface regions of the plastic housing compound.

A further aspect of the invention relates to a semiconductor module witha semiconductor base component and at least one semiconductor componentstacked on top of it, the semiconductor base component of the stackbeing a semiconductor component in accordance with the explanationsgiven above. A semiconductor base component of this type has theadvantage that semiconductor components using BGA housing technologyand/or LBGA housing technology can be stacked on top of one another in aspace-saving manner. For this purpose, it is merely necessary to providethe plastic housing compound with corresponding metallic inclusions, orto prepare a corresponding conduction path structure on the plasticouter sides of the semiconductor component, in order for this then to bethickened by means of a solder technology to form correspondinginterconnects.

In a further embodiment of the invention, the stacked semiconductorcomponent has surface-mountable contacts. Components of this type havingsurface-mountable outer contacts have hitherto been stackable only ifsurface-mountable outer contacts of this type are arranged in the edgeregions of the semiconductor components to be stacked. With thesemiconductor component according to the invention, which can be usedhere as a semiconductor base component, it is possible to providesurface-mountable outer contacts for the stacked semiconductor componentto be distributed evenly over its underside.

It is therefore also possible to provide modern memory components usingBGA and/or LBGA housing technology in the semiconductor component, inwhich case it is preferable for the memory components provided to beDRAMs and/or GDRAMs. This has the advantage that it is possible toincrease the storage capacity and storage density in order thereby torealize memory components which have a storage capacity of severalgigabits.

In a further preferred embodiment of the invention, it is provided thatthe semiconductor module comprises at least one logic component,preferably an MPCP (microprocessor chip package) and a memory component,preferably a DRAM (dynamic random access memory) or a GDRAM (graphicdynamic random access memory). On account of the compact design of thesemiconductor module according to the invention in the form of asemiconductor component stack, it is possible to provide memory moduleswhich allow a high access rate in the gigahertz range.

A process for producing a semiconductor component with a plastic housingwhich has outer interconnects, via which lower outer contact surfacesand upper outer contact surfaces are electrically connected, comprisesthe following process. After a semiconductor component with a plastichousing is produced, a structure of conduction paths which can be wettedby liquid solder material is realized on the plastic outer surfaces ofthe housing along the housing contour between the lower outer contactsurfaces and the upper outer contact surfaces. Finally, a solder depositis applied to the upper outer contact surfaces. Then, the soldermaterial of the solder deposit is liquefied, and it wets or coats theprepared conduction paths with solder material and in the process formsouter interconnects for connecting the lower outer contact surfaces tothe upper outer contact surfaces.

This process has the advantage that a base semiconductor component whichfunctions reliably and is suitable for stacking semiconductor modulescan be created using simple mechanisms and a process which can beimplemented on an industrial scale. In this context, a core point of theprocess is the production of structures which realize conduction pathsthat can be wetted by liquid solder material on the plastic outer sides.For this purpose, in a preferred implementation example of the process,a correspondingly high proportion of electrically conductive particleswhich are wettable by solder material is admixed to the plastic housingcompound.

Electrically conductive particles of this type may be the metallicconstituents of an organometal compound or electrically conductivenanoparticles, such fullerenes or carbon nanotubes, or alternativelylarge crystal particles, of a size of a few micrometers, which are addedto the plastic housing compound as metallic filler. If materials of thistype are present in the plastic housing compound, it is possible for thestructure of conduction paths which can be wetted by liquid soldermaterial to be produced on the plastic outer surfaces of the housingbetween lower outer contact surfaces and upper outer contact surfaces byradiation treatment. The partial uncovering of the metallicallyconducting inclusions in the plastic compound in the region of theconduction paths can be achieved by radiation by photons, ions and/orelectrons. This may involve partial evaporation of the plastic housingcompound to uncover the electrically conducting inclusions. On the otherhand, in particular in the case of organometal compounds, it is possibleto expose the metal atoms by thermal irradiation.

In a further preferred implementation example of the process accordingto the invention, to produce a structure of conduction paths which canbe wetted by liquid solder material, it is possible to selectively applya metal layer, which is a few nanometers thick and can be wetted byliquid solder material, to plastic outer surfaces of the housing betweenlower outer contact surfaces and upper outer contact surfaces.Sputtering techniques, vapor deposition techniques and/or plasmadeposition techniques can be used for this purpose, the intention beingfor the plastic outer sides of the housing which are not to be coveredby the metal layer to be protected from coating with metal by aphotolithography technique carried out on a photoresist structure.

The outer contact surfaces on the top side of the plastic housing can beused to apply the solder deposits, from which the interconnects are thenformed along the conductor paths. After the solder material of thesolder deposits has been liquefied, these solder deposits wet theconducting particles of the conduction paths and coat the conductionpaths to form interconnects of solder material. The solder deposits canadvantageously be applied to the outer contact surfaces on the top sideof the plastic housing at low cost by dispensing, jet printing orstencil printing.

To summarize, the process of the invention can produce a semiconductorbase component which facilitates the stacking of semiconductor modules,provides great flexibility for the customer when using semiconductorchips from various manufacturers, and alleviates the problem of havingto discard an entire module if individual semiconductor chips aredefective by virtue of the fact that it is now possible for individualsemiconductor components to be removed in order for a module to berepaired. Furthermore, the subject matter of the invention has theadvantage that it is possible to use extremely thin semiconductor chips,with a thickness of a few tens of micrometers, and extremely minimalmold caps.

Further, interconnects can be produced on the outer side of a plastichousing at low cost by sputtering or a laser patterning process ofconductive particles present in the plastic housing compound or byexternal bonding wire connection. In this case, it is advantageouslypossible to use inexpensive standard process, which means that there isno need for a complex technology involving through-contacts through thesemiconductor chip or through the plastic housing compound. Furthermore,there is no need for an electroplating process, which is standard forother semiconductor base components, since in this case, to produceelectrical connections between the outer contact surfaces of the wiringsubstrate and the top side of the plastic housing, a reliable electricalconnection can advantageously be created by simple positioning of solderdeposits.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a diagrammatic cross section through a semiconductorcomponent with plastic housing, which along its housing outer contourshas conduction paths of a first embodiment of the invention.

FIG. 2 shows a diagrammatic cross section through a semiconductorcomponent with plastic housing, which along its housing outer contourshas conduction paths of a second embodiment of the invention.

FIG. 3 shows a diagrammatic cross section through a semiconductorcomponent with plastic housing, which has solder deposits on the topside of the housing and has conduction paths as shown in FIG. 1 or FIG.2 on its edge sides.

FIG. 4 shows a diagrammatic cross section through a semiconductorcomponent as shown in FIG. 3 after the solder material of the solderdeposits has spread out along the conduction paths as shown in FIG. 1 orFIG. 2.

FIG. 5 shows a diagrammatic cross section through a semiconductorcomponent stack which includes a semiconductor component as shown inFIG. 4 as semiconductor base component and also a stacked semiconductorcomponent with surface-mountable outer contacts.

DETAILED DESCRIPTION

FIG. 1 shows a diagrammatic cross section through a semiconductorcomponent I with a plastic housing 3, which along its housing outercontours 33 has conduction paths 11 of a first embodiment of theinvention. In this first embodiment of the invention, these conductionpaths 11 are not continuous metal strips, but rather compriseindividual, electrically conducting inclusions 22 and/or spots that areisolated from one another and can be wetted by a solder material. Inthis first embodiment of the conduction paths 11, these wettable pointsof the interconnects are formed by virtue of the plastic 21 of thehousing 3 having electrically conducting particles 12, preferably withmetallic constituents 23, which are distributed through the volume ofthe plastic compound 32 and have been uncovered along the predeterminedconduction paths 11 on the plastic outer surfaces 4 of the housing 3 bysuitable processing.

Between the conduction paths 11, the plastic outer surfaces 4 remainunaffected by the uncovering step, so that the conduction paths 11, ofwhich in this instance two extend from the top side 8 of the plastichousing 3 along the edge sides 34 and 35 as far as contact terminalsurfaces 36 of a substrate 15 which supports the plastic housing. Theareal extent of the substrate 15 is larger than that of a semiconductorchip 37 which is electrically connected to through-contacts 17 of thewiring substrate 15 by way of flip chip contacts 39. Thethrough-contacts 17 of the substrate 15 have lower outer contactsurfaces 5 on the underside 6 of the plastic housing 3, whichsimultaneously forms the underside 19 of the wiring substrate 15.

The lower outer contact surfaces 5 are connected via a wiring structure20 to through-contacts 17 in the edge regions 16 of the wiring substrate15. Therefore, the contact terminal surfaces 36 on the edge sides 16 ofthe wiring substrate 15 form a node at which the conduction paths 11,the outer contact surfaces 5 and the flip chip contacts 39 areelectrically connected to one another by way of the through-contacts 17arranged in the edge sides 16. In this first embodiment, however, theconduction paths 11 do not yet provide an electrical connection from thecontact terminal surfaces 36 of the wiring substrate 15 to the top side8 of the housing 3 while the conduction paths 11 and their electricallyconducting inclusions or particles are not electrically connected toform interconnects.

FIG. 2 shows a diagrammatic cross section through a semiconductorcomponent I with plastic housing 3 which has conduction paths 41 of asecond embodiment of the invention along its housing outer contours 33.Components with the same functions as in FIG. 1 are denoted by the samereference numerals and are not explained further. In this embodiment ofthe conduction paths 41, the latter have a thin metal layer 14 which isa few nanometers thick and are arranged in a conductor path structure 13on the top side 8 of the housing 3 and on the edge sides 34 and 35 ofthe housing 3. On the top side 8 of the housing 3, the conduction paths41 have upper outer contact surfaces 7 on their ends and extend beyondthe edge sides 34 and 35 as far as contact terminal surfaces 36, whichare arranged on the top side 18 of the wiring substrate 15 in the edgeregions 16.

FIG. 3 shows a diagrammatic cross section through a semiconductorcomponent I with plastic housing 3, which has solder deposits 31 on thetop side 8 of the housing 3 and has conduction paths 11 as shown in FIG.I or 41 as shown in FIG. 2 on its edge sides 34 and 35. These solderdeposits 31 may be limited to the top outer contact surfaces 7 of thesemiconductor material or, as shown in FIG. 3, may also extend over theentire conduction path structure 13 on the top side 8 of the housing 3.These solder deposits 31 can be applied using various techniques,preferably by a stencil printing technique or by jet printingtechnology.

The distribution of the solder material over the conduction pathstructure 13 can be carried out for the entire conduction path structure13 in a suitable furnace, in which the solder deposit 31 is melted andthe solder material is distributed uniformly along the conduction pathstructure 13 on the conduction paths 41. To promote the uniformdistribution of the solder material, the edge sides 34 and 35 areinclined with respect to the horizontal, preferably with an angle ofinclination α of <60°.

FIG. 4 shows a diagrammatic cross section through a semiconductorcomponent I as shown in FIG. 3 after the solder material of the solderdeposits 31 has spread out along the conduction paths 11 or 41 as shownin FIGS. I or 2, respectively. Components with the same functions as inthe preceding figures are denoted by the same reference numerals and arenot explained again.

On account of the solder material spreading out along the conductionpaths 11 or 41, as shown in FIG. I or FIG. 2, respectively, outerinterconnects 9 comprising a layer of solder 10 have now formed on theconduction paths 11 or 41. The outer interconnects 9 extend from upperouter contact surfaces 7 as far as the contact terminal surfaces 36, onwhich minimal new solder deposits 40 have formed. These solder deposits40 on the contact terminal surfaces 36 on the top side 18 of the wiringsubstrate 15 are responsible for intensive contact between the outerinterconnects 9 on the plastic outer surfaces 4 of the plastic housing 3and the contact terminal surfaces 36 of the wiring substrate 15.Therefore, the outer upper outer contact surfaces 7 are electricallyconnected to the lower outer contact surfaces 5 via the through-contacts17 and a wiring structure 20 on the underside 19 of the wiring substrate15.

Since the lower outer contact surfaces 5 are connected to flip chipcontacts 39 of the semiconductor chip 37 via through-contacts 17, thesemiconductor component I according to the invention provides thepossibility of using this semiconductor component 1 as the basesemiconductor component for a stack of semiconductor components. Forthis purpose, it is advantageous that the upper outer contact surfaces 7can be arranged in any desired way on the top side 8 of the plastichousing 3 and their size can be matched to outer contacts of asemiconductor component which is to be stacked.

FIG. 5 shows a diagrammatic cross section through a semiconductorcomponent stack 2, which as semiconductor base component 26 has asemiconductor component I as shown in FIG. 4 and also has a stackedsemiconductor component 25 with a semiconductor chip 38 and withsurface-mountable outer contacts 24. This semiconductor stack 2 forms asemiconductor module 28 of a logic component 29, which on its edgeregions of the underside 42 has the outer contacts 24. The upper outercontact surfaces 7 of the outer interconnects 9 of the semiconductorbase component 26 are arranged in a corresponding way. In thissemiconductor module 28, the semiconductor base component 26 is formedby a memory component 30, which is electrically connected to the stackedsemiconductor component 25 via the outer interconnects 9.

Having described preferred embodiments of new and improved semiconductorcomponent with a plastic housing, and corresponding process forproducing the semiconductor component, it is believed that othermodifications, variations and changes will be suggested to those skilledin the art in view of the teachings set forth herein. It is therefore tobe understood that all such variations, modifications and changes arebelieved to fall within the scope of the present invention as defined bythe appended claims. Although specific terms are employed herein, theyare used in a generic and descriptive sense only and not for purposes oflimitation.

1. A method for producing a semiconductor component with a plastichousing including outer interconnects that electrically connect lowerouter contact surfaces and upper outer contact surfaces, the methodcomprising: producing a semiconductor component with a plastic housing;producing a structure of conduction paths on plastic outer surfaces ofthe housing along an outer contour of the housing between the lowerouter contact surfaces and the upper outer contact surfaces, theconduction paths being wettable by liquid solder material; applyingsolder deposits to the upper outer contact surfaces; and liquefying thesolder material of the solder deposits so as to wet and coat theconductions paths with solder material to form outer interconnectsbetween the lower outer contact surfaces and the upper outer contactsurfaces.
 2. The method of claim 1, further comprising: admixingparticles that are wettable by liquid solder material to a plasticcompound to produce a structure of the conduction paths that is wettableby liquid solder material.
 3. The method of claim 1, further comprising:admixing inclusions of nanoparticles to a plastic compound to produce astructure of the conduction paths that is wettable by liquid soldermaterial.
 4. The method of claim 1, further comprising: admixinginclusions of an organometal compound to a plastic compound to produce astructure of the conduction paths that is wettable by liquid soldermaterial.
 5. The method of claim 1, further comprising: irradiating theplastic outer surfaces with photons, ions and/or electrons to produce astructure of the conduction paths that is wettable by liquid soldermaterial.
 6. The method of claim 1, further comprising: bonding outerbonding wires to produce a structure of the conduction paths that iswettable by liquid solder material.
 7. The method of claim 1, furthercomprising: selectively applying a metal layer that is wettable byliquid solder material to plastic outer surfaces of the housing betweenthe lower outer contact surfaces and the upper outer contact surfaces toproduce a structure of the conduction paths that is wettable by liquidsolder material.
 8. The method of claim 7, further comprising: applyingthe metal layer by sputtering, vapor deposition, and/or plasmadeposition and patterning the metal layer via photolithography to formconductor paths.
 9. The method of claim 1, wherein the solder depositsare applied by dispensing, jet printing, or stencil printing.